A closeup of the primary tool used to map hydrothermal
plumes. A ring of plastic sampling bottles surrounds the CTD, an electronic
package that monitors seawater Conductivity, Temperature, and Depth. The
bottles are closed on command from the ship, usually when a scientist
monitoring the sensors sees strong evidence of a plume. The CTD carries
other sensors that measure optical light backscattering, seawater pH and
Eh, and other chemical species. Pictured here are Ed Baker (left) and
Cornel deRonde (right).